New study links childhood cat ownership to schizophrenia later in life

A new study finds a link between childhood cat ownership and schizophrenia in adulthood but doctors warn that more research needs to be done before parents panic. (Getty)

New research finds that living with cats as a child might be a risk factor for developing mental disorders such as schizophrenia, and scientists think a tiny single-celled organism called Toxoplasma gondii might offer an explanation.

“Toxo,” as it’s often called, is one of the most prevalent parasites, infecting some 60 million Americans, according to the Centers for Disease Control, and, by some estimates, half the world population. It’s also widespread in many species of mammals and birds, and has a unique relationships with cats.

The parasite can only reproduce inside the bodies of cats and this works to their advantage because toxo helps them catch prey. When toxo infects rodents, scientists have learned their response to cats is altered and they lose their natural fear of felines.

Humans can get toxo by accidentally ingesting cat feces and this can happen when changing a cat’s litter box or ingesting contaminated soil (e.g., not washing hands after gardening or eating unwashed fruits or vegetables from a garden). This is only a concern during a short window of a few weeks after the cat first becomes infected with the parasite but because cats rarely show symptoms when they become infected, their owners have no way of knowing. People also become infected by drinking contaminated water or eating undercooked meat.

For most healthy children and adults, toxo doesn’t cause any clear problems because the immune system usually prevents the parasite from causing illness. Scientists suspect the parasite remains in the body and becomes dormant. But pregnant women should take precaution because toxo increases the risk of miscarriage and birth defects. Also, a few studies have found an association between the parasite and an increased incidence of mental disorders.

This latest study published in the June edition of the journal Schizophrenia Researchcompared two previous studies finding a link between cat ownership in childhood with the development of schizophrenia later in life with an unpublished survey on mental health from 1982, CBS News reports.

“The results were the same, suggesting that cat ownership in childhood is significantly more common in families in which the child later becomes seriously mentally ill,” he team from Johns Hopkins Univeristy concluded.

Dr. Hayden Schwenk, a pediatric infectious disease specialist at Lucile Packard Children’s Hospital at Stanford, says this study should not put parents with cats at home into a panic.

“There may be an association but that doesn’t mean there’s causation,” Schwenk explained to SFGate. “The study isn’t showing a direct link between toxoplasma and mental illness and the study authors are saying further research needs to be done.”

Also, Dr. Schwenk points out, “Lots of people own cats and schizophrenia is a relatively uncommon illness.”

Dr. Lisa Dana, a pediatrician at Golden Gate Pediatrics in Mill Valley and San Francisco, agrees that further research needs to be done before parents consider abandoning their cats, but she says that it never hurts to be cautious. “I would not have children change the kitty litter, and I would cover sandboxes when not in use,” Dr. Dana told SFGate. “I would also be cautious at playgrounds with sand. Especially in areas with large feral cat populations. I know in San Francisco, many playgrounds have moved away from using sand. These preventive steps may make a difference.”

Dr Dana added that the most important thing for the public to know is that toxoplasmosis can have severe consequences in people with compromised immune systems and pregnant women.